Loss Per Share - Calculation of Basic and Diluted Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Jan. 31, 2023	Jan. 31, 2022	Oct. 31, 2022
Numerator
Net loss attributable to FuelCell Energy, Inc.	$ (18,622)	$ (40,624)	$ (40,624)
Preferred dividends - Series B	(800)	(800)	(800)
Net loss attributable to common stockholders	$ (19,422)	$ (41,424)	$ (41,424)
Denominator
Weighted average common shares outstanding - basic	405,803,753	366,734,739	366,734,739
Weighted average common shares outstanding - diluted	405,803,753	366,734,739	366,734,739
Net loss to common stockholders per share - basic	$ (0.05)	$ (0.11)	$ (0.11)
Net loss to common stockholders per share - diluted	$ (0.05)	$ (0.11)	$ (0.11)
Series B Preferred Stock
Numerator
Preferred dividends - Series B	$ (800)	$ (800)